Evaluation of Olfactory Impairment in Parkinson’s Disease Using Near-Infrared Spectroscopy

Evaluation of Olfactory Impairment in Parkinson’s Disease Using Near-Infrared Spectroscopy

Karaki Masayuki (Kagawa University, Japan), Kobayashi Eiji (Kagawa University, Japan), Touge Tetsuo (Kagawa University, Japan) and Mori Nozomu (Kagawa University, Japan)
DOI: 10.4018/978-1-4666-2113-8.ch030
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Hyposmia, psychiatric disorders, and cognitive problems are common non-motor manifestations of Parkinson’s disease (PD), but how they are related to the progression of PD remains unclear. Olfactory dysfunction, which is a common non-motor symptom of Parkinson’s disease, is considered to be an early manifestation of this disease. The aim of this study is to investigate the usefulness of near-infrared spectroscopy (NIRS) in measuring olfaction in PD patients and to establish the cortical basis of olfactory function in PD patients. This study was conducted on 9 healthy normosmic volunteers and 24 patients with PD. The authors employed a 22-channel NIRS device with eight light-incident fibers and seven light-detection fibers and placed fibers every 2.5 cm on the forehead of volunteers. Isovaleric acid was used as the odor stimulant. The authors measured the changes in total hemoglobin (tHb) concentration from baseline values and compared the results obtained from healthy normosmic volunteers with those from PD patients. PD patients had higher scores in the subjective olfactory test and smaller changes in tHb concentrations compared with normal volunteers. In particular, no changes in tHb concentration were detected in patients with the awareness of the sense of smell disorder.
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Participants comprised 24 patients with idiopathic PD (14 men and 10 women; mean age = 66.1 years) and 9 age-matched healthy volunteers who had not complained of any olfactory impairments (6 men and 3 women; mean age = 62.0 years). All patients were examined for naso-sinus diseases by sinus CT or MRI. Patients with nasal or paranasal sinus disease or with a history of olfactory diseases, post virus infective olfactory disorder, or head injury were excluded from the study.

Information documents and the Informed Consent Forms were approved by the Institutional Review Board, Faculty of Medicine, Kagawa University before being used (Approval No.: Heisei 21-52, Institutional Review Board, Faculty of Medicine, Kagawa University). Consents were obtained from the subjects after the Investigator or Sub-investigator explained the details of the study using the information documents. Participating patients submitted written consent of their own free will after it was confirmed that they understood the explanations sufficiently. When submitting the consent, the person in charge of the explanation put his/her seal or signature and date on the Consent Form.

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